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USGS-Alaska Volcano Observatory
Distinct seismic and sonic signals accompany volcanic unrest. By analogy with light, these signals often exist on the lower frequency or red end of the spectrum. The identification and interpretation of low frequency signals poses a challenge for volcano monitoring, since earthquake processing systems are tuned to most reliably detect high frequency seismicity. In this talk, I present examples of low frequency seismicity observed during eruptions at Alaskan volcanoes and discuss the insights into magmatic systems derived from these signals. I further demonstrate long-range detection of low frequency sound waves, or infrasound, generated by volcanic explosions and its utility for real-time alarms. I end with an analysis of five unusual low frequency earthquakes recently observed at Little Sitkin Volcano, Alaska, that were precursory (4-6 days prior) to the beginning of a shallow earthquake swarm beneath the volcano.
Host Greg Waite
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